316 
WATURE 
[Aug. 17, 1871 

‘open ocean where there was a prevalence of winds in a cer- 
tain direction over one part of it, it seemed necessary that the 
currents produced by that wind should be as Dr. Carpenter had 
maintained. The only case in which he could conceive of a re- 
turn along the bottom produced by wind was one of great 
interest, but in which the circumstances were precisely opposite 
to those of an open oceanic circulation, viz. in the case of a frith 
or fiord. The elevations of 6, §, or 10 feet, which we know 
result from high wind, must be thus explained; the return 
circulation cannot but be along the bottom. In the case of a 
frith, if the whole surface is carried up in a current, the water 
must get away somewhere. . If there were a strong breeze in 
narrow waters when the whole surface was broken up, there 
would be a great deal of surface drift ; but even without break- 
ing up a surface there was a current necessarily accompanying 
waves at sea when the height of the wave was not infinitesimal, 
z.e., when it was not very small in comparison with the length ; 
sometimes there was a great surface current amounting to three 
or four knots in these circumstances, and there must be an equal 
outflow atthe bottom. Dr. Carpenter’s explanation of the ver- 
tical circulation seemed to make the whole thing perfectly clear. 
Ocean currents were altogether unknown, with the exception of 
a few isolated cases, and even regarding these the knowledge was 
not nearly practical enough for the ordinary purposes of navi- 
gation. In the operations of 1866 to recover the cable of 1865, 
it was discovered that the success or non success altogether de- 
pended on the management of the ocean current. Captain 
Moriarty, who was chiefly concerned in finding the ship’s place, 
came to the conclusion that the whole subject of ocean currents 
ought to be made a matter of hydrography, and certainly it was 
an object of all others appropriate to a nautical country. The 
question of temperature was also of great practical importance, 
as the temperature of the sea bottom along which the cable was 
to be laid was of enormous importance to the enterprise. If a 
cable showed certain signs at 49° F. it was good, if it showed the 
same signs at 40° F. it was bad. Another most serious practical 
want was to know precisely the temperature of the cable when 
laid, in order that if there was a fault its temperature might be 
accurately determined. 
Prof. Stokes said that if he had risen first, he would have 
pointed out what had been so well stated by Sir W. Thom- 
son, that the only case in which a vertical circulation could 
be produced in the horizontal blow forward by wind, was in the 
case of a narrow channel. If a portion of a widely-extended 
ocean were blown on by the wind, the water would be propelled 
forward, but the tendency would be to take it in from all direc- 
tions, not merely from one, so that the inflow would be lost in 
minuteness. That a surface-current is a necessary accompani- 
ment of waves, seemed pretty obvious. If waves are already in 
existence on the surface of water, it is evident that their backs 
must be more strongly acted on than their fronts by the wind ; 
there must be a horizontal resultant forward which must push on 
the water somehow or other ; the fact of the existence of these 
waves implied that there was already a surface current of a 
certain amount. 
Mr. Robert Russell said he could only go a certain distance 
with Dr. Carpenter ; he considered the effect of polar cold and 
equatorial heat to be comparatively small compared with the 
wind. The Atlantic itself narrows so much towards the North 
Pole, that its vast surface is forced by the south-west wind 
to the northern ocean, and is forced into it in spite of polar cold. 
Prof. G. C. Foster said that a possible cause of the formation 
of currents was the coexistence of different specific gravities in 
neighbouring quantities of water. 
Dr. Carpenter said it gave him great satisfaction to hear the 
general agreement of Sir W. Thomson with the views that he 
had advanced ; he had expressly spoken of the open ocean, and 
mentioned as excepted such cases as the Gibraltar current. 
With regard to cables, Capt. Sherard Osborne had mentioned to 
him that the cable recently laid down in the Eastern seas towards 
China was generally in shallow water and therefore warm, so as 
to diminish the conducting power of the wire, but at one point 
it dipped down into a hole, and there the temperature having 
fallen the conducting power was greatly improved. Everyone 
knew that when the cable was cut and buoyed in 1865, there 
was a long wire rope with a buoy attached to it. It got adrift, 
and was seen by an Atlantic mail steamer ro° to the southward. 
One wouid have expected it to the North-East, through the in- 
fluence of the Gulf Stream. It was suggested that the long rope 
had broken away at the bottom ; that its long tail was hanging 
in the sea, and the action of the great lower movement to the 

south might have been stronger on the tail than the action of the 
surface water on the upper portion of the rope. 
Mr. Buchan said that the Scottish Meteorological Society were 
conducting investigations which would settle what were the winds 
and currents over each degree of a portion of the Atlantic. 
Mr. Scott said he hoped to give Mr. Buchan charts of the 
currents over the area such as were never before possessed. 
They were derived from all available sources of information. 
Sir W. Thomson said it seemed demonstrable that in all water 
above five or ten fathoms deep, the current under return due to 
surface drift was insensibly small, and he thought that this de- 
monstrated Dr. Carpenter’s statement, that the main current 
could not be produced by wind, though the wind might produce 
very considerable surface currents. 
Prof. Colding, who stated he had been working at the same 
subject for many years since, made some remarks on the effect of 
the earth’s rotation on the currents, and 
Prof. Tait remarked that the discussion well illustrated the 
use of the British Association. 
Observations Physiques en Ballon, by M. Janssen. 
SECTION B. 
THISs section did not sit on Saturday, and on Monday the 
proceedings commenced with two short papers by the Presi- 
dent, Dr. Andrews, Ox the Dichroism of the Vapour of Todine 
and on the Action of Heat on Bromine. The fine purple colour 
of the vapour of iodine arises from its transmitting freely the red 
and blue rays of the spectrum, while it absorbs nearly the whole 
of the green rays. The transmitted light passes freely through 
a red copper or a blue cobalt glass. But if the iodine vapour be 
sufficiently dense, the whole of the red rays are absorbed, and 
the transmitted rays are of a pure blue colour. They are now 
freely transmitted as before by the cobalt glass, but will not pass 
through the red glass. The solution of iodine in bisulphide of 
carbon exhibits a similar dichroism, and according to its density 
appears either purple or blue when white light is transmitted 
through it. The alcoholic solution, on the contrary, is of a red 
colour, and does not exhibit any dichroism. If a fine tube be 
filled one half with liquid bromine and one half with vapour of 
bromine, and after being hermetically sealed, is gradually heated 
until the temperature is above the critical point, the whole of the 
bromine becomes quite opaque, and the tube has the aspect of 
being filled with a dark red and opaque resin. A measure of the 
change of power of transmitting light in this case may be ob- 
tained by varying the proportion of liquid and vapour in the tube. 
Even liquid bromine transmits much less light when heated 
strongly in a hermetically sealed tube than in its ordinary state. 
In connection with this subject, Mr. Dewar exhibited an experiment 
illustrating ihe action of light upon peroxide of chiorine. 
The report on the Utilisation of Sewage was presented by Mr. 
Grantham. It was divided under the following heads ;—(1) 
Experiments on Britton’s Farm, Mr. Hope. (2) Comparison of 
results during winter of Croydon, Norwood, and Britton’s Farm 
experiments, Dr. Corfield. (3) Report on Analysis in connection 
with above, Dr. Corfield. (4) Upward Filtration of Sewage at 
Ely, Dr. Corfield. (5) Phosphate Process, Dr. Corfield. (6) Dry- 
Earth System at Lancaster, Drs. Corfield and Gilbert. Dr, 
Bischof read a paper Ox the Examination of Water for Sanitary 
Purposes, in which he sought to show that the appearance of the 
residue obtained by evaporation when seen under the microscope 
afforded a ready method of detecting sewage contamination. 
Dr. Otto Richter contributed a paper On ‘he Chemical Constitu- 
tion of Glycollic Alcohol and its Heterologues as viewed in the light 
of the Typo-nucleus Theory. The Abbé Moigno gave an account 
of the history and working of the photographic post, and ex- 
hibited a number of collodion films containing microscopic photo- 
graphs of letters and despatches. Every film reproduced twelve 
or sixteen folio pages of printing, and contained on an average 
3,000 despatches. The whole of the official and private 
despatches came by pigeons during the investment of Paris, num- 
bered about 115,000, weighing in all about two grammes. 
Dr. Wright gave an account of some experiments On ‘he 
Essential Oil of Orange Peel. Ut has been shown that this oil 
consists principally of a hydrocarbon, hesperidene, C,,)H,,, and 
an amorphous resin of the formula C,,H ,O03. When hesperi- 
dene is boiled ‘‘ per ascensum ” with sulphuric acid and potassium 
bichromate, carbon dioxide is slowly evolved, and acetic acid 
produced, whence it is inferred that the structure of the hydro- 
carbon is CH, 
CH (C,H,,).” 

r= | 
